Hippo dances with hormones

Fruit fly researchers find connections between the Hippo growth control pathway and the steroid hormone ecdysone; implications for cancer/stem cell biology?

Microbiome enthusiasm at Emory

Microbiome research is expanding at Emory. May this Clostidium difficile bacterium (image courtesy of CDC) not dominate your microbiome.

Hypersomnia update: clarithromycin study

"The benefit observed is large enough to be clinically meaningful," but lots of caveats to consider. First double-blind, placebo-controlled study of a GABA-targeting drug in hypersomnia. Artwork originally from 2013 Emory Medicine story of an early hypersomnia patient.

Cancer

Hippo dances with hormones

Although fruit flies don’t develop cancer, cancer and stem cell researchers have been learning a great deal from fruit flies – in particular, mutant flies with overgrown organs that resemble hippopotamuses.

A fly gene called Hippo and its relatives in mammals normally block cell proliferation and limit organ size. When flies have mutations in Hippo or other genes (together dubbed the Hippo pathway), the resulting overgrowth distorts their tissues into hippopotamus-like bulges. See Figure 3 of this review for an example. In humans, the Hippo pathway is involved in forming embryonic stem cells, suppressing cancerous growth, and also in regenerative growth and wound healing..

Working with flies, researchers at Emory have found that the abnormal growth induced by Hippo pathway disruption depends on genes involved in responding to the steroid hormone ecdysone.

Their results were published Thursday, July 2 in Developmental Cell.

“Ecdysone is, to some degree, the fly version of estrogen,” says senior author Ken Moberg, PhD, associate professor of cell biology at Emory University School of Medicine.

Ecdysone

In fly larvae, ecdysone triggers metamorphosis, in which adult structures such as wings and eyes emerge from small compartments called imaginal discs.. Ecdysone has a chemical structure like that of estrogen, testosterone and other steroid hormones found in humans. Ecdysone is not sex-specific, but it acts with the same mechanism as other steroid hormones, diffusing into cells and binding proteins that bind DNA and regulate gene activity. Read more

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Promising probe for detecting recurrent prostate cancer

Part of the new Winship magazine feature on prostate cancer focuses on a PET imaging probe called FACBC, which was developed by radiologists at Emory. 18F-FACBC (anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid, also called “fluciclovine”) has a lengthening track record in detecting recurrent prostate cancer.

Structure of FACBC, from patent application.

Usually in PET imaging, radioactive glucose is injected into the body, and since cancer cells have a sweet tooth, they take up a lot of the radioactive tracer. But plenty of the tracer also appears in the urine, complicating prostate cancer detection efforts, since the prostate is so close to the bladder. In contrast, FACBC is readily taken up by prostate cancer cells, but doesn’t appear as much in urine.

Because of space considerations, we did not include David Schuster’s description of how FACBC’s utility in prostate was first discovered. Several years ago, he and Mark Goodman had begun investigating the probe’s potential in imaging brain tumors and kidney tumors, and used it with a patient with a large renal mass and many enlarged lymph nodes, as described in the radiology newsletter Aunt Minnie. Read more

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Why checkpoint inhibitors fall short for some types of cancer

The big news from the recent American Society of Clinical Oncology meeting has been largely about immunotherapy drugs, also known as checkpoint inhibitors. These drugs have been shown to be effective in prolonging life in patients with some types of cancer, such as lung cancer and melanoma, but not others, such as colorectal and prostate cancer.

Lab Land asked oncologist Bradley Carthon and immunology researcher Haydn Kissick why. Both Carthon’s clinical work and Kissick’s lab research on prostate cancer are featured in the new issue of Winship magazine, but the prostate feature just touches on checkpoint inhibitors briefly.

Carthon says the reason checkpoint inhibitors haven’t moved the needle with prostate cancer is “likely due to the absence of infiltration of the prostatic tissue by tumor-associated lymphocytes.”

Checkpoint inhibitors are supposed to unleash the immune system, but if the immune cells aren’t in contact with the cancer cells so that the drugs can spur them into action, they won’t help much. Carthon says: “The answer may be to ‘prime’ the prostate with an agent, then introduce the checkpoint inhibitors.” Read more

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Moving urology beyond the PSA test

The PSA (prostate specific antigen) blood test has been criticized for years for driving men to seek biopsies and then definitive treatment for slow-growing cancers that may not pose a danger.

At the recent AUA meeting in New Orleans, urologist Martin Sanda presented results from research on tests that could allow the urology field to move beyond the PSA test as it is now. Winship magazine’s cover story has more on this topic.

Martin Sanda, MD is director of Winship Cancer Institute’s Prostate Cancer Program and chair of urology at Emory University School of Medicine

Right now, only about a sixth of men who have a biopsy based on the results of a PSA test have something that doctors agree should be called a cancer (a tumor with a Gleason score of seven or higher).

Sanda described studies on a urine test that could double that specificity, possibly eliminating unnecessary biopsies for many men. Read more

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Honokiol, Jack of all trades

Emory dermatologist Jack Arbiser discovered the anti-angiogenic properties of honokiol, a compound derived from magnolia cones, more than a decade ago. Since then, honokiol has been found to have anti-inflammatory, anti-oxidant and anticancer properties.

A paper published Tuesday in Nature Communications from researchers at the University of Chicago shows that honokiol inhibits the mitochondrial enzyme Sirt3, which has connections to longevity. Manesh Gupta and colleagues demonstrate that honokiol can block cardiac hypertrophy in mice, a finding with possible relevance for the treatment of heart failure.

Sirt3 has been linked both genetically to human life span, and until now, the only way to increase levels of Sirt3 was old-fashioned calorie restriction and/or endurance exercise.

The authors write: It is believed that Sirt3 does not play a role in embryonic development, but rather it fine tunes the activity of mitochondrial substrates by lysine deacetylation to protect cells from stress… To the best of our knowledge, this is the first report describing a pharmacological activator of Sirt3.

 

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Low doses of imatinib can stimulate innate immunity

Low doses of the anti-cancer drug imatinib can spur the bone marrow to produce more innate immune cells to fight against bacterial infections, Emory and Winship Cancer Institute researchers have found.

The results were published this week in the journal PLOS Pathogens.

The findings suggest imatinib, known commercially as Gleevec, or related drugs could help doctors treat a wide variety of infections, including those that are resistant to antibiotics, or in patients who have weakened immune systems. The research was performed in mice and on human bone marrow cells in vitro, but provides information on how to dose imatinib for new clinical applications.

“We think that low doses of imatinib are mimicking ‘emergency hematopoiesis,’ a normal early response to infection,” says senior author Daniel Kalman, PhD, associate professor of pathology and laboratory medicine at Emory University School of Medicine.

Imatinib, is an example of a “targeted therapy” against certain types of cancer. It blocks tyrosine kinase enzymes, which are dysregulated in cancers such as chronic myelogenous leukemia and gastrointestinal stromal tumors.

Imatinib also inhibits normal forms of these enzymes that are found in healthy cells. Several pathogens – both bacteria and viruses – exploit these enzymes as they transit into, through, or out of human cells. Researchers have previously found that imatinib or related drugs can inhibit infection of cells by pathogens that are very different from each other, including tuberculosis bacteria and Ebola virus. Read more

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Who regulates the regulators? Drosha

MicroRNAs have emerged as important master regulators in cells, since each one can shut down several target genes. Riding on top of the master regulators is Drosha, the RNA-cutting enzyme that initiates microRNA processing in the nucleus. Drosha and its relative Dicer have been attracting attention in cancer biology, because they are thought to be behind a phenomenon where cancerous cells can “infect” their healthy neighbors via tiny membrane-clothed packets called exosomes.

At Emory, pharmacologist Zixu Mao and colleagues recently published in Molecular Cell their findings that Drosha is regulated by stress (experimentally: heat or peroxide) through p38 MAP kinase.

Although we mention relevance to cancer above, this is one of those basic cell biology findings that may have applicability to several areas of medicine. Alterations in miRNA processing have been linked to neurodegenerative disease (Fragile X-associated tremor/ataxia syndrome, for one example). MicroRNA-packed exosomes are also being studied by biomedical engineers as potential therapeutic tools in regenerative medicine, so knowing what cellular stress does to miRNA production could be useful. Read more

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BAI1: a very multifunctional protein

Everything is connected, especially in the brain. A protein called BAI1 involved in limiting the growth of brain tumors is also critical for spatial learning and memory, researchers have discovered.

Mice missing BAI1 have trouble learning and remembering where they have been. Because of the loss of BAI1, their neurons have changes in how they respond to electrical stimulation, and subtle alterations in parts of the cell needed for information processing.

The findings may have implications for developing treatments for neurological diseases, because BAI1 is part of a protein regulatory network neuroscientists think is connected with autism spectrum disorders.

The results were published online March 9 in Journal of Clinical Investigation.

Erwin Van Meir, PhD, and his colleagues at Winship Cancer Institute of Emory University have been studying BAI1 (brain-specific angiogenesis inhibitor 1) for several years. Part of the BAI1 protein can stop the growth of new blood vessels, which growing cancers need. Normally highly active in the brain, the BAI1 gene is lost or silenced in brain tumors, suggesting that it acts as a tumor suppressor.

The researchers were surprised to find that the brains of mice lacking the BAI1 gene looked normal anatomically. They didn’t develop tumors any faster than normal, and they didn’t have any alterations in their blood vessels, which the researchers had anticipated based on BAI1’s role in regulating blood vessel growth. What they did have was problems with spatial memory.

Read more

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Explainer: oncolytic viruses

A recent publication from Bill Kaiser’s and Ed Mocarski’s labs in Cell Host & Microbe touches on a concept that needs explaining: oncolytic viruses.

Viruses have been subverting the machinery of healthy cells for millions of years, and many viruses tend to infect particular tissues or cell types. So they are a natural starting point for researchers to engineer oncolytic viruses, which preferentially infect and kill cancer cells.

Several oncolytic viruses have progressed to advanced clinical trials. Amgen’s “T-Vec”, a modified herpes simplex virus, could be the first to be approved by the FDA this year based on its efficacy against metastatic melanoma.  Read more

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Nox4 inhibitor expands its reach to A-T

Emory dermatologist Jack Arbiser has been investigating (and recently patented) inhibitors of the enzyme Nox4 as potential anti-cancer drugs.

Nox4 has emerged as a potential therapeutic target in ataxia-telangiectasia, a rare multifaceted genetic disorder that leads to neurological problems, a weakened immune system and an increased risk of cancer. Ataxia-telangiectasia (or A-T) is caused by a defect in ATM, a sensor responsible for managing cells’ responses to DNA damage and other kinds of stress.

In a February PNAS paper, researchers at the National Cancer Institute led by William Bonner report that a Nox4 inhibitor can dial back oxidative stress and DNA damage in ataxia-telangiectasia cells, and can reduce cancer rates in a mouse model of the disease. Nox4 was activated in cells and tissue samples obtained from A-T patients.

The Nox4 inhibitor the NCI team used, fulvene-5, was originally identified by Arbiser in a 2009 Journal of Clinical Investigation paper as a possible treatment for hemangiomas, a common tumor in infants that emerges from blood vessels.

David Lambeth, an expert on the NADPH oxidase family of enzymes, and his team recently described Nox4 as an “hydrogen peroxide-generating oxygen sensor.”

 

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